Sensor units are widely used for detecting physical quantities (such as, for example, temperature, current, pressure, strain or the like) of various objects to be detected. For example, vehicles such as passenger cars or the like are generally equipped with one or more microprocessors (MPUs) for electronically controlling various parts in order to improve their performance and/or efficiency and reliability. Precisely, electronically controlled in passenger cars are not only engine controls such as timings of fuel injection, ignition and pressure inside cylinders but also open/close operation of doors, angle adjustments of back mirrors, etc.
In such electronic controls, when instructions or commands are outputted from such MPU, it is necessary to confirm actual operations by feeding back to the MPU whether electrical signals are properly supplied to motors or actuators or any malfunctions are caused. For this end, passenger cars or the like are typically equipped with a plurality of sensor units to detect physical quantities such as, for example, the magnitude of electrical currents flowing through various conductors as well as temperatures or the like to affect their operations.
Generally, sensor units are manufactured as unitary units by integrating sensors (for example, Hall elements) for detecting current, temperature, pressure or the like) and associated electronic circuits using semiconductor integrated circuit (IC) technologies in order to reduce manufacturing cost and improve reliability. Moreover, in order to achieve miniaturization and high density of such sensor units, it is preferable or essential that such sensor units are operable with lower power supply voltage and have minimum number of terminals, i.e., only three terminals (power terminal, ground terminal and signal output terminal) for interconnection with external devices. It is also typical that such sensor units have no internal power supply but are designed to receive operation power supply voltage from outside through their power supply terminals.
Most sensors, for example, Hall elements are not only affected by external temperature, pressure, strain or the like but also have aging characteristics (i.e., degradation due to hours of operation) no exception. Especially, those integral sensors manufactured using IC technologies tend to be largely affected by external conditions and have larger aging characteristics because they are manufactured by densely packing a plurality of parts and components. In order to minimize such adverse effects and providing stable detection signal from such sensor units, it is necessary to provide correction or calibration means and memories (for example, nonvolatile memories) for properly calibrating detection signals from the sensors based on the correction data pre-stored in such memories.
Proposed are techniques for writing data in a nonvolatile memory of an IC sensor unit including a sensor and a nonvolatile memory and reading such data from an external host device. An integrated circuit arrangement is disclosed to supply a voltage level (for example, +8V) that is sufficiently higher than the normal operating voltage (for example, +5V) to the power supply terminal for parameterize the IC (see, for example, Patent Document 1 and Patent Document 2 below). Also disclosed are component communication circuit and method for externally inputting a trigger pulse in superimposed with a power supply voltage to a power supply terminal for supplying an operation voltage and detecting a data superimposed with its analog output signal from its output terminal using a data detector (see, for example Patent Document 3 below). Also disclosed are an IC having a mixed signal single wire and a method of operating the same, wherein the IC comprises a power supply terminal, a ground terminal and an output terminal to enable selectively outputting an analog signal and a control signal from the output terminal based on a control signal from an additional terminal (see, for example, Patent Document 4 below). Furthermore, disclosed are signal calibration device and method including a sensor, a signal processor and a data storage for storing a correction data to be entered into the processor, and having three terminals of a power terminal, a ground terminal and an output terminal, for enabling to write a calibration data into the data storage from the output terminal together with an output signal from the sensor (see, for example, Patent Document 5 below).
Also disclosed are inertia velocity sensor and method having a power supply terminal and an output terminal and including built-in test means for conditioning such as a programming mode or the like by way of a path other than the output terminal (see, for example, Patent Document 6 below).